Alight source unit that is provided in an interior part of a vehicle includes an LED unit (a light source) and a light guide member that guides light from the LED unit to illuminate surroundings thereof. In the light source unit, the LED is housed in the LED unit and an end portion of the light guide member is inserted to a connecting portion of the LED unit.
Usually, the light source and the light guide member are integrally provided as the light source unit first, and then, the light source unit is mounted to an interior part of a vehicle. However, the light source unit integrally including the light source and the light guide member is relatively great in size and this causes problems in easy handling and deteriorates operability in mounting of the light source unit. After the light source and the guide member are integrally provided as the light source unit, the light source unit is mounted to the interior part of a vehicle. Therefore, an order of the mounting steps for mounting the light source unit to the interior part is not freely determined.